Porous membranes are widely used for a variety of applications depending on their properties such as the material used for making said membranes, their morphology and the size of the membrane pores. Said membranes can be used as filtration membranes, separation membranes, membrane adsorbers, membrane catalysts or membrane bioreactors. The fields of application include nanotechnology, food science, energy, environment, health, chemicals, biotechnologies and medicine.
In general, porous membranes are obtained by sintering organic or inorganic materials or by track-etching process. Porous membrane can also be prepared by stretching polymer films. These films are extruded from a polymer powder at high temperatures of from 100 to 250° C. which are close to melting temperature as described in U.S. 60/293,301 and U.S. Pat. No. 3,351,495A. The extruded films are then annealed, cooled and stretched. Matrix membranes are very often prepared by sol-gel method to synthetize silica particle in-situ within polymer solution, followed by phase separation. One of the drawbacks of these procedures is the use of considerable solvent volumes. Said solvents are not recoverable which is detrimental for the workers, the environment but also increases the costs of said membranes.
Porous membranes of the prior art are generally single use membranes. To re-use a membrane, it should be washed under acid and/or oxidative conditions to ensure elimination of all molecules and/or residues from a previous use. Membranes known to date show severe loss of integrity when washed under acid and/or oxidative conditions.
Given the wide use of porous membranes, membranes with specific surface properties, functionalized with specific ligands, increased robustness, able to resist to solvents and/or to various cleaning agents and/or able to endure extreme pH conditions are strongly required. There is also a need for washable and reusable membranes.
The object of the invention is to overcome at least part of the above mentioned problems. One of the aims of the invention is to provide reusable porous membranes where specific functionalities can be added easily. Another object is to provide membranes having long-term resistant to extremely acidic and oxidative conditions and/or to a large variety of solvents. Another object is to provide a process for the production of porous membranes which is economical and environment-friendly. These objects are achieved in accordance with the invention as described in the claims.